In the field of implantable medical devices, implantable cardioverter/defibrillators (ICD), implantable pulse generators (IPG) and pacemaker/cardioverter/defibrillators (PCD) provide sensing of arrhythmias and programmable staged therapies including pacing regimens and cardioversion energy and defibrillation energy shock regimens in order to terminate a sensed arrhythmia with the most energy efficient and minimally traumatic therapies. In such implantable medical devices, the atrial and ventricular pacing pulse generators, sense amplifiers and associated timing operations are incorporated into a system having atrial and ventricular pace/sense medical electrical leads.
A wide variety of such pace/sense and defibrillation leads have been proposed for positioning endocardially within a heart chamber or associated blood vessel or epicardially about the heart chambers or more remotely in subcutaneous locations. Typically, the leads bear pace/sense/defibrillation electrodes with associated lead conductors and connector elements all of which are either incorporated into a single pacing lead body or into a combined pacing and defibrillation lead body. At least two electrodes are required to define a current pathway encompassing a heart chamber to be paced or defibrillated.
In such implantable medical device systems, the integrity of the medical electrical leads is of great importance. Lead insulation breaches, interior lead conductor wire fracture or fractures with other lead parts have been known to occur. Generally, the leads are constructed of small diameter, highly flexible, lead bodies made to withstand degradation by body fluids. In addition, the leads must be able to function in the presence of dynamic body environments that apply chemical and physical stress and strain to the lead body and the connections made to electrodes or sensor terminals. Some of these stresses may occur during the implantation process. Months or years later, porosity that developed from those stresses may be magnified by exposure to body fluids. These, in turn, may result in conductor or insulation related conditions that may be manifested in an intermittent or sudden Loss of Capture (LOC), out-of-range impedance and/or Loss of Sensing (LOS).
Several approaches have been suggested to provide physicians with information and/or expeditious detection or prevention of the factors affecting lead integrity. Examples of those approaches are set forth in U.S. Pat. No. 4,140,131 (Dutcher et al.); U.S. Pat. No. 4,549,548 (Wittkampf et al.); U.S. Pat. No. 4,606,349 (Livingston et al.); U.S. Pat. No. 4,899,750 (Ekwall); U.S. Pat. No. 5,003,975 (Hafelfinger et al.); U.S. Pat. No. 5,137,021 (Wayne et al.); U.S. Pat. No. 5,156,149 (Hudrlik); U.S. Pat. No. 5,184,614 (Collins); U.S. Pat. No. 5,201,808 (Steinhaus et al.); U.S. Pat. No. 5,201,865 (Kuehn); U.S. Pat. No. 5,224,475 (Berg et al.); U.S. Pat. No. 5,344,430 (Berg et al.); U.S. Pat. No. 5,350,410 (Kieks et al.); U.S. Pat. No. 5,431,692 (Hansen et al.); U.S. Pat. No. 5,453,468 (Williams et al.); U.S. Pat. No. 5,507,786 (Morgan et al.); U.S. Pat. No. 5,534,018 (Walhstrand et al.); U.S. Pat. No. 5,549,646 (Katz et al.); U.S. Pat. No. 5,722,997 (Nedungadi et al.); U.S. Pat. No. 5,741,311 (McVenes et al.); U.S. Pat. No. 5,755,742 (Schuelke et al.); and U.S. Pat. No. 5,814,088 (Paul et al.). All of these patents are incorporated herein by reference.
Many of the solutions discussed in the aforementioned systems have employed periodic testing that includes measurements of parameters such as lead impedance to determine when the integrity of the medical electrical lead is compromised. One of the challenges associated with the lead checks is that the periodic measurements may not always correlate with the intermittent nature of the conductor make-break contact. Additionally, the periodic measurements and measurements triggered by apparent physiological signal aberrations may not identify lead-related conditions expeditiously for effective containment and to prevent error propagation. A system is needed that will support continuous real-time lead monitoring and containment of detected lead-related conditions to prevent error propagation that may lead to adverse system impact.